scholarly journals Biodegradation of the Allelopathic Chemical Pterostilbene by a Sphingobium sp. Strain from the Peanut Rhizosphere

2018 ◽  
Vol 85 (5) ◽  
Author(s):  
Ri-Qing Yu ◽  
Zohre Kurt ◽  
Fei He ◽  
Jim C. Spain
Keyword(s):  
Pathogenic Fungi ◽  
Bacterial Degradation ◽  
Ecological Role ◽  
Microbial Infection ◽  
Catabolic Pathway ◽  
Content Type ◽  
Dead End ◽  
Initial Cleavage ◽  
Bacterial Interference

ABSTRACT Many plants produce allelopathic chemicals, such as stilbenes, to inhibit pathogenic fungi. The degradation of allelopathic compounds by bacteria associated with the plants would limit their effectiveness, but little is known about the extent of biodegradation or the bacteria involved. Screening of tissues and rhizosphere of peanut (Arachis hypogaea) plants revealed substantial enrichment of bacteria able to grow on resveratrol and pterostilbene, the most common stilbenes produced by the plants. Investigation of the catabolic pathway in Sphingobium sp. strain JS1018, isolated from the rhizosphere, indicated that the initial cleavage of pterostilbene was catalyzed by a carotenoid cleavage oxygenase (CCO), which led to the transient accumulation of 4-hydroxybenzaldehyde and 3,5-dimethoxybenzaldehyde. 4-Hydroxybenzaldehyde was subsequently used for the growth of the isolate, while 3,5-dimethoxybenzaldehyde was further converted to a dead-end metabolite with a molecular weight of 414 (C24H31O6). The gene that encodes the initial oxygenase was identified in the genome of strain JS1018, and its function was confirmed by heterologous expression in Escherichia coli. This study reveals the biodegradation pathway of pterostilbene by plant-associated bacteria. The prevalence of such bacteria in the rhizosphere and plant tissues suggests a potential role of bacterial interference in plant allelopathy. IMPORTANCE Pterostilbene, an analog of resveratrol, is a stilbene allelochemical produced by plants to inhibit microbial infection. As a potent antioxidant, pterostilbene acts more effectively than resveratrol as an antifungal agent. Bacterial degradation of this plant natural product would affect the allelopathic efficacy and fate of pterostilbene and thus its ecological role. This study explores the isolation and abundance of bacteria that degrade resveratrol and pterostilbene in peanut tissues and rhizosphere, the catabolic pathway for pterostilbene, and the molecular basis for the initial cleavage of pterostilbene. If plant allelopathy is an important process in agriculture and management of invasive plants, the ecological role of bacteria that degrade the allelopathic chemicals must be equally important.

scholarly journals Resveratrol as a Growth Substrate for Bacteria from the Rhizosphere

2018 ◽  
Vol 84 (10) ◽  
Author(s):  
Zohre Kurt ◽  
Marco Minoia ◽  
Jim C. Spain
Keyword(s):  
Antioxidant Properties ◽  
Physiological Role ◽  
Bacterial Degradation ◽  
Ecological Role ◽  
Plant Metabolites ◽  
Natural Habitats ◽  
Content Type ◽  
Secondary Plant Metabolites ◽  
Degrading Bacteria

ABSTRACT Resveratrol is among the best-known secondary plant metabolites because of its antioxidant, anti-inflammatory, and anticancer properties. It also is an important allelopathic chemical widely credited with the protection of plants from pathogens. The ecological role of resveratrol in natural habitats is difficult to establish rigorously, because it does not seem to accumulate outside plant tissue. It is likely that bacterial degradation plays a key role in determining the persistence, and thus the ecological role, of resveratrol in soil. Here, we report the isolation of an Acinetobacter species that can use resveratrol as a sole carbon source from the rhizosphere of peanut plants. Both molecular and biochemical techniques indicate that the pathway starts with the conversion of resveratrol to 3,5-dihydroxybenzaldehyde and 4-hydroxybenzaldehyde. The aldehydes are oxidized to substituted benzoates that subsequently enter central metabolism. The gene that encodes the enzyme responsible for the oxidative cleavage of resveratrol was cloned and expressed in Escherichia coli to establish its function. Its physiological role in the resveratrol catabolic pathway was established by knockouts and by the reverse transcription-quantitative PCR (RT-qPCR) demonstration of expression during growth on resveratrol. The results establish the presence and capabilities of resveratrol-degrading bacteria in the rhizosphere of the peanut plants and set the stage for studies to evaluate the role of the bacteria in plant allelopathy. IMPORTANCE In addition to its antioxidant properties, resveratrol is representative of a broad array of allelopathic chemicals produced by plants to inhibit competitors, herbivores, and pathogens. The bacterial degradation of such chemicals in the rhizosphere would reduce the effects of the chemicals. Therefore, it is important to understand the activity and ecological role of bacteria that biodegrade resveratrol near the plants that produce it. This study describes the isolation from the peanut rhizosphere of bacteria that can grow on resveratrol. The characterization of the initial steps in the biodegradation process sets the stage for the investigation of the evolution of the catabolic pathways responsible for the biodegradation of resveratrol and its homologs.

scholarly journals Functional Redundancy of Linuron Degradation in Microbial Communities in Agricultural Soil and Biopurification Systems

2016 ◽  
Vol 82 (9) ◽  
pp. 2843-2853 ◽  
Author(s):  
Benjamin Horemans ◽  
Karolien Bers ◽  
Erick Ruiz Romero ◽  
Eva Pose Juan ◽  
Vincent Dunon ◽  
...  
Keyword(s):  
Agricultural Soil ◽  
Bacterial Consortium ◽  
Bacterial Degradation ◽  
Catabolic Gene ◽  
Bacterial Populations ◽  
Content Type ◽  
Respective Contribution ◽  
On Farm ◽  
Biopurification Systems

ABSTRACTThe abundance oflibA, encoding a hydrolase that initiates linuron degradation in the linuron-metabolizingVariovoraxsp. strain SRS16, was previously found to correlate well with linuron mineralization, but not in all tested environments. Recently, an alternative linuron hydrolase, HylA, was identified inVariovoraxsp. strain WDL1, a strain that initiates linuron degradation in a linuron-mineralizing commensal bacterial consortium. The discovery of alternative linuron hydrolases poses questions about the respective contribution and competitive character ofhylA- andlibA-carrying bacteria as well as the role of linuron-mineralizing consortia versus single strains in linuron-exposed settings. Therefore, dynamics ofhylAas well asdcaQas a marker for downstream catabolic functions involved in linuron mineralization, in response to linuron treatment in agricultural soil and on-farm biopurification systems (BPS), were compared with previously reportedlibAdynamics. The results suggest that (i) organisms containing eitherlibAorhylAcontribute simultaneously to linuron biodegradation in the same environment, albeit to various extents, (ii) environmental linuron mineralization depends on multispecies bacterial food webs, and (iii) initiation of linuron mineralization can be governed by currently unidentified enzymes.IMPORTANCEA limited set of different isofunctional catabolic gene functions is known for the bacterial degradation of the phenylurea herbicide linuron, but the role of this redundancy in linuron degradation in environmental settings is not known. In this study, the simultaneous involvement of bacteria carrying one of two isofunctional linuron hydrolysis genes in the degradation of linuron was shown in agricultural soil and on-farm biopurification systems, as was the involvement of other bacterial populations that mineralize the downstream metabolites of linuron hydrolysis. This study illustrates the importance of the synergistic metabolism of pesticides in environmental settings.

Is the literature on content analysis of intellectual capital reporting heading towards a dead end?

2015 ◽  
Vol 16 (3) ◽  
pp. 681-699 ◽  
Author(s):  
Viktoria Goebel
Keyword(s):  
Content Analysis ◽  
Intellectual Capital ◽  
Content Type ◽  
Dead End ◽  
Content Analyses ◽  
New Ideas ◽  
Highly Correlated ◽  
Research Frameworks ◽  
Meta Analyses

Purpose – The purpose of this paper is to respond to the call by Dumay and Cai (2014) for new ideas to enhance intellectual capital (IC) research. One possibility is to draw conclusions on comparability across the results of prior studies. This study investigates whether the results of prior IC content analyses are comparable despite differences in their IC research frameworks. Design/methodology/approach – A content analysis of 428 German management reports is conducted, capturing the IC reporting scores for individual IC items to investigate the role of certain widely used IC items. The relationships of IC scores for different combinations of widely used IC items are further examined in a correlation analysis to indicate comparability of prior results. Findings – The findings show that widely used IC items capture the majority of IC reporting and that the IC scores for different combinations of these IC items are highly correlated. These findings indicate that the results of prior IC content analyses are comparable as long as most of the widely used IC items are included in prior IC research frameworks. Research limitations/implications – The study contributes to IC reporting research as it shows that conclusions can be drawn across prior studies in meta-analyses because the results of prior studies are comparable in rankings and key findings. Originality/value – Although content analyses of IC reporting have been previously criticised, this study seminally questions the comparability of the results of prior studies due to differences in the IC research frameworks.

scholarly journals Identification and Characterization of a Tetramethylpyrazine Catabolic Pathway in Rhodococcus jostii TMP1

2013 ◽  
Vol 79 (12) ◽  
pp. 3649-3657 ◽  
Author(s):  
Simonas Kutanovas ◽  
Jonita Stankeviciute ◽  
Gintaras Urbelis ◽  
Daiva Tauraite ◽  
Rasa Rutkiene ◽  
...  
Keyword(s):  
Expression Profiles ◽  
Bacterial Degradation ◽  
Ring Cleavage ◽  
Published Data ◽  
Catabolic Pathway ◽  
Genome Database ◽  
Content Type ◽  
Intermediate Metabolites ◽  
Inducible Protein ◽  
Rhodococcus Jostii

ABSTRACTAt present, there are no published data on catabolic pathways ofN-heterocyclic compounds, in which all carbon atoms carry a substituent. We identified the genetic locus and characterized key reactions in the aerobic degradation of tetramethylpyrazine inRhodococcus jostiistrain TMP1. By comparing protein expression profiles, we identified a tetramethylpyrazine-inducible protein of 40 kDa and determined its identity by tandem mass spectrometry (MS-MS)de novosequencing. Searches against anR. jostiiTMP1 genome database allowed the identification of the tetramethylpyrazine-inducible protein-coding gene. The tetramethylpyrazine-inducible gene was located within a 13-kb genome cluster, denominated the tetramethylpyrazine degradation (tpd) locus, that encoded eight proteins involved in tetramethylpyrazine catabolism. The genes from this cluster were cloned and transferred into tetramethylpyrazine-nondegradingRhodococcus erythropolisstrain SQ1. This allowed us to verify the function of thetpdlocus, to isolate intermediate metabolites, and to reconstruct the catabolic pathway of tetramethylpyrazine. We report that the degradation of tetramethylpyrazine is a multistep process that includes initial oxidative aromatic-ring cleavage by tetramethylpyrazine oxygenase, TpdAB; subsequent hydrolysis by (Z)-N,N′-(but-2-ene-2,3-diyl)diacetamide hydrolase, TpdC; and further intermediate metabolite reduction by aminoalcohol dehydrogenase, TpdE. Thus, the genes responsible for bacterial degradation of pyrazines have been identified, and intermediate metabolites of tetramethylpyrazine degradation have been isolated for the first time.

scholarly journals Role of IncP-1β Plasmids pWDL7::rfpand pNB8c in Chloroaniline Catabolism as Determined by Genomic and Functional Analyses

2011 ◽  
Vol 78 (3) ◽  
pp. 828-838 ◽  
Author(s):  
J. E. Król ◽  
J. T. Penrod ◽  
H. McCaslin ◽  
L. M. Rogers ◽  
H. Yano ◽  
...  
Keyword(s):  
Single Copy ◽  
Degradation Pathway ◽  
Bacterial Degradation ◽  
Ring Cleavage ◽  
Close Relative ◽  
Broad Host Range ◽  
Content Type ◽  
Aromatic Ring Cleavage ◽  
Functional Analyses

ABSTRACTBroad-host-range catabolic plasmids play an important role in bacterial degradation of man-made compounds. To gain insight into the role of these plasmids in chloroaniline degradation, we determined the first complete nucleotide sequences of an IncP-1 chloroaniline degradation plasmid, pWDL7::rfpand its close relative pNB8c, as well as the expression pattern, function, and bioaugmentation potential of the putative 3-chloroaniline (3-CA) oxidation genes. Based on phylogenetic analysis of backbone proteins, both plasmids are members of a distinct clade within the IncP-1β subgroup. The plasmids are almost identical, but whereas pWDL7::rfpcarries a duplicate inverted catabolic transposon, Tn6063, containing a putative 3-CA oxidation gene cluster,dcaQTA1A2BR, pNB8c contains only a single copy of the transposon. No genes for an aromatic ring cleavage pathway were detected on either plasmid, suggesting that only the upper 3-CA degradation pathway was present. ThedcaA1A2Bgene products expressed from a high-copy-number vector were shown to convert 3-CA to 4-chlorocatechol inEscherichia coli. Slight differences in thedcapromoter region between the plasmids and lack of induction of transcription of the pNB8cdcagenes by 3-CA may explain previous findings that pNB8C does not confer 3-CA transformation. Bioaugmentation of activated sludge with pWDL7::rfpaccelerated removal of 3-CA, but only in the presence of an additional carbon source. Successful bioaugmentation requires complementation of the upper pathway genes with chlorocatechol cleavage genes in indigenous bacteria. The genome sequences of these plasmids thus help explain the molecular basis of their catabolic activities.

scholarly journals pH Signaling in Human Fungal Pathogens: a New Target for Antifungal Strategies

2014 ◽  
Vol 13 (3) ◽  
pp. 342-352 ◽  
Author(s):  
Muriel Cornet ◽  
Claude Gaillardin
Keyword(s):  
Mammalian Cells ◽  
Drug Targets ◽  
Fungal Pathogens ◽  
Synergistic Effects ◽  
Pathogenic Fungi ◽  
Antifungal Drugs ◽  
Drug Pressure ◽  
Fungal Virulence ◽  
Content Type

ABSTRACTFungi are exposed to broadly fluctuating environmental conditions, to which adaptation is crucial for their survival. An ability to respond to a wide pH range, in particular, allows them to cope with rapid changes in their extracellular settings. PacC/Rim signaling elicits the primary pH response in both model and pathogenic fungi and has been studied in multiple fungal species. In the predominant human pathogenic fungi, namely,Candida albicans,Aspergillus fumigatus, andCryptococcus neoformans, this pathway is required for many functions associated with pathogenesis and virulence. Aspects of this pathway are fungus specific and do not exist in mammalian cells. In this review, we highlight recent advances in our understanding of PacC/Rim-mediated functions and discuss the growing interest in this cascade and its factors as potential drug targets for antifungal strategies. We focus on both conserved and distinctive features in model and pathogenic fungi, highlighting the specificities of PacC/Rim signaling inC. albicans,A. fumigatus, andC. neoformans. We consider the role of this pathway in fungal virulence, including modulation of the host immune response. Finally, as now recognized for other signaling cascades, we highlight the role of pH in adaptation to antifungal drug pressure. By acting on the PacC/Rim pathway, it may therefore be possible (i) to ensure fungal specificity and to limit the side effects of drugs, (ii) to ensure broad-spectrum efficacy, (iii) to attenuate fungal virulence, (iv) to obtain additive or synergistic effects with existing antifungal drugs through tolerance inhibition, and (v) to slow the emergence of resistant mutants.

scholarly journals Single-cell genomics-based analysis reveals a vital ecological role of Thiocapsa sp. LSW in the meromictic Lake Shunet, Siberia

2021 ◽  
Vol 7 (12) ◽  
Author(s):  
Yu-Ting Wu ◽  
Pei-Wen Chiang ◽  
Kshitij Tandon ◽  
Denis Yu Rogozin ◽  
Andrey G. Degermendzhy ◽  
...  
Keyword(s):  
Single Cell ◽  
Anoxygenic Phototrophic Bacteria ◽  
Sequencing Analysis ◽  
Ecological Role ◽  
Meromictic Lakes ◽  
Purple Sulfur Bacterium ◽  
Single Cell Genomics ◽  
Content Type ◽  
Link Type

Meromictic lakes usually harbour certain prevailing anoxygenic phototrophic bacteria in their anoxic zone, such as the purple sulfur bacterium (PSB) Thiocapsa sp. LSW (hereafter LSW) in Lake Shunet, Siberia. PSBs have been suggested to play a vital role in carbon, nitrogen and sulfur cycling at the oxic–anoxic interface of stratified lakes; however, the ecological significance of PSBs in the lake remains poorly understood. In this study, we explored the potential ecological role of LSW using a deep-sequencing analysis of single-cell genomics associated with flow cytometry. An approximately 2.7 Mb draft genome was obtained based on the co-assembly of five single-cell genomes. LSW might grow photolithoautotrophically and could play putative roles not only as a carbon fixer and diazotroph, but also as a sulfate reducer/oxidizer in the lake. This study provides insights into the potential ecological role of Thiocapsa sp. in meromictic lakes.

Toxin-producing endosymbionts shield pathogenic fungus against micropredators

2022 ◽  
Author(s):  
Ingrid Richer ◽  
Silvia Radosa ◽  
Zoltan Cseresnyes ◽  
Iluiia Ferling ◽  
Hannah Buettner ◽  
...  
Keyword(s):  
Pathogenic Fungus ◽  
Pathogenic Fungi ◽  
Rice Seedling ◽  
Phytopathogenic Fungus ◽  
Ecological Role ◽  
Seedling Blight ◽  
Rhizopus Microsporus ◽  
Fungal Host ◽  
Amoebicidal Effect

The phytopathogenic fungus Rhizopus microsporus harbours a bacterial endosymbiont (Mycetohabitans rhizoxinica) for the production of the toxin rhizoxin, the causative agent of rice seedling blight. This toxinogenic bacterial-fungal alliance is, however, not restricted to the plant disease, but has been detected in numerous environmental isolates from geographically distinct sites covering all five continents. Yet, the ecological role of rhizoxin beyond rice seedling blight has been unknown. Here we show that rhizoxin serves the fungal host in fending off protozoan and metazoan predators. Fluorescence microscopy and co-culture experiments with the fungivorous amoeba Protostelium aurantium revealed that ingestion of R. microsporus spores is toxic to P. aurantium. This amoebicidal effect is caused by the bacterial rhizoxin congener rhizoxin S2, which is also lethal towards the model nematode Caenorhabditis elegans. By combining stereomicroscopy, automated image analyses, and quantification of nematode movement we show that the fungivorous nematode Aphelenchus avenae actively feeds on R. microsporus that is lacking endosymbionts, while worms co-incubated with symbiotic R. microsporus are significantly less lively. This work uncovers an unexpected ecological role of rhizoxin as shield against micropredators. This finding suggests that predators may function an evolutionary driving force to maintain toxin-producing endosymbionts in non-pathogenic fungi.

scholarly journals Colanic Acid Intermediates PreventDe NovoShape Recovery of Escherichia coli Spheroplasts, Calling into Question Biological Roles Previously Attributed to Colanic Acid

2016 ◽  
Vol 198 (8) ◽  
pp. 1230-1240 ◽  
Author(s):  
Dev K. Ranjit ◽  
Kevin D. Young
Keyword(s):  
Escherichia Coli ◽  
Cell Wall ◽  
Shape Recovery ◽  
Initial Step ◽  
Content Type ◽  
Colanic Acid ◽  
Dead End ◽  
Peptidoglycan Cell Wall ◽  
Normal Shape

ABSTRACTAfter losing their protective peptidoglycan, bacterial spheroplasts can resynthesize a cell wall to recreate their normal shape. InEscherichia coli, this process requires the Rcs response. In its absence, spheroplasts do not revert to rod shapes but instead form enlarged spheroids and lyse. Here, we investigated the reason for this Rcs requirement. Rcs-deficient spheroids exhibited breaks and bulges in their periplasmic spaces and failed to synthesize a complete peptidoglycan cell wall, indicating that the bacterial envelope was defective. To determine the Rcs-dependent gene(s) required for shape recovery, we tested spheroplasts lacking selected RcsB-regulated genes and found that colanic acid (CA) biosynthesis appeared to be involved. Surprisingly, though, extracellular CA was not required for recovery. Instead, lysis was caused by mutations that interrupted CA biosynthesis downstream of the initial glycosyl transferase, WcaJ. DeletingwcaJprevented lysis of spheroplasts lacking ensuing steps in the pathway, and providing WcaJ intransto a mutant lacking the entire CA operon triggered spheroplast enlargement and lysis. Thus, CA is not required for spheroplast recovery. Instead, CA intermediates accumulate as dead-end products which inhibit recovery of wall-less cells. The results strongly imply that CA may not be required for the survivalE. coliL-forms. More broadly, these findings mandate that previous conclusions about the role of colanic acid in biofilm formation or virulence must be reevaluated.IMPORTANCEWall-less bacteria can resynthesize their walls and recreate a normal shape, which inEscherichia colirequires the Rcs response. While attempting to identify the Rcs-dependent gene required for shape recovery, we found that colanic acid (CA) biosynthesis appeared to be involved. Surprisingly, though, cell death was caused by mutations that interrupted CA biosynthesis downstream of the initial step in the pathway, creating dead-end compounds that inhibited recovery of wall-less cells. When testing for the biological role of CA, most previous experiments used mutants that would accumulate these deadly intermediates, meaning that all prior conclusions must be reexamined to determine if the results were caused by these lethal side effects instead of accurately reflecting the biological purpose of CA itself.

scholarly journals Lipopeptide Interplay Mediates Molecular Interactions between Soil Bacilli and Pseudomonads

2021 ◽  
Author(s):  
Sofija Andrić ◽  
Thibault Meyer ◽  
Augustin Rigolet ◽  
Claire Prigent-Combaret ◽  
Monica Höfte ◽  
...  
Keyword(s):  
Molecular Interactions ◽  
Plant Immunity ◽  
Bioactive Metabolites ◽  
Soil Conditions ◽  
Ecological Role ◽  
Interspecies Interactions ◽  
Bacillus Velezensis ◽  
Model Species ◽  
Content Type

Plant-associated Bacillus velezensis and Pseudomonas spp. represent excellent model species as strong producers of bioactive metabolites involved in phytopathogen inhibition and the elicitation of plant immunity. However, the ecological role of these metabolites during microbial interspecies interactions and the way their expression may be modulated under naturally competitive soil conditions has been poorly investigated.

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